FireFoam what is HRR ?

fgal · April 14, 2010, 14:58

Hi OpenFoamers,

Does anybody knows what the volumic scalar field HRR is? Because I thought that it was the combustion source term in the energy equation but it is sometimes negative.

Is it divided by the cell volume, because it can raise values around+/- 1E6 ?

Many thanks

Francois Gallard

fgal · April 16, 2010, 10:37

Hi, I found this in the fireFoam source code :
HRR=
- fvc::ddt(rho, hc)
- fvc::div(phi, hc)
+ fvc::laplacian(turbulence->alphaEff(), hc);

So it seems that the HRR is defined as all the source terms in the enthalpy equation except for the heat Fourier and turbulent diffusions. So, if I am right, source terms left are :
- heat due to chemistery
- heat due to friction, certainly close to zero because of very low Mach number of the flow
- radiated heat, but I swiched the radiation off
- inter spieces diffusion term, zero because all heat capacities are supposed to be equals
-the pressure term, very low

So I still don't understand why the heat release rate can be negative and positive depending on the cells, with so huge variations : -1E6 ; +1E6

Has anybody an idea ?

April 14, 2010, 14:58	FireFoam what is HRR ?	#1
fgal Member Francois Gallard Join Date: Mar 2010 Location: Toulouse, France Posts: 43 Rep Power: 16	Hi OpenFoamers, Does anybody knows what the volumic scalar field HRR is? Because I thought that it was the combustion source term in the energy equation but it is sometimes negative. Is it divided by the cell volume, because it can raise values around+/- 1E6 ? Many thanks Francois Gallard

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
fireFoam and basicThermo	prapanj	OpenFOAM Running, Solving & CFD	26	November 8, 2016 07:47
DNS, FireFoam, adaptive mesh	fgal	OpenFOAM Running, Solving & CFD	3	July 5, 2010 13:09

April 16, 2010, 10:37		#2
fgal Member Francois Gallard Join Date: Mar 2010 Location: Toulouse, France Posts: 43 Rep Power: 16	Hi, I found this in the fireFoam source code : HRR= - fvc::ddt(rho, hc) - fvc::div(phi, hc) + fvc::laplacian(turbulence->alphaEff(), hc); So it seems that the HRR is defined as all the source terms in the enthalpy equation except for the heat Fourier and turbulent diffusions. So, if I am right, source terms left are : - heat due to chemistery - heat due to friction, certainly close to zero because of very low Mach number of the flow - radiated heat, but I swiched the radiation off - inter spieces diffusion term, zero because all heat capacities are supposed to be equals -the pressure term, very low So I still don't understand why the heat release rate can be negative and positive depending on the cells, with so huge variations : -1E6 ; +1E6 Has anybody an idea ?